The present invention relates to a metal cutting insert that is primarily intended for turning operations.
For all sorts of turning operations, there is a certain interplay between the feed rate and the corner radius, the corner radius being the connection between the main cutting edge and the secondary cutting edge. The surface fineness produced on the workpiece is specifically influenced by the interplay between the corner radius and the feed rate. The approach angle is defined as the angle between the main cutting edge and the direction of feed. This angle has a considerable influence on the interrelation between the different cutting force components, and thereby also on the surface fineness and dimension accuracy. Surface fineness and dimension accuracy are very sensitive to changes of the approach angle. One problem for all turning operations is to obtain the desired surface fineness. Another problem is poor tool life.
Embodiments of prior cutting inserts are shown in EP 1226892 A2 and DE 10308234 A1.
It is desirable to provide a cutting insert that improves the fineness of the machined surface.
It is desirable to provide a cutting insert that significantly improves tool life.
Still another object of the present invention is to provide a cutting insert that improves surface finish over the total tool life.
It is desirable to provide a cutting insert that reduces influence on residual stresses in the work piece surface.
It is desirable to provide a cutting insert that reduces influence on hardness in the workpiece surface.
It is desirable to provide a cutting insert that reduces the sensitivity of a turning cutting insert relative to the positioned approach angle.
It is desirable to provide a cutting insert that reduces the radial forces during turning.
It is desirable to provide a cutting insert that reduces provides for a smaller variation in cutting edge position when used in a tool holder.
According to an aspect of the present invention, a cutting insert for turning comprises an upper surface, a lower surface substantially parallel with the upper surface, and at least three side surfaces extending between the upper and lower surfaces, a transition between two adjacent side surfaces forming a rounded nose radius surface at a cutting insert cutting corner. The cutting insert comprises a peripheral land bridging the upper and side surfaces at least at the cutting corner at a chamfer angle, and an intersection of the land and the nose radius surface forming a nose cutting edge, the nose cutting edge being defined by at least one radius. The cutting corner comprises at least one curved wiper edge. A chamfer angle in a cross-section at the nose cutting edge is larger than a chamfer angle in a cross-section a distance away from the nose cutting edge and the peripheral land in a plan view has a substantially constant width.